Patterns of Blood Flow to the Uterus and Ovaries of Ewes during the Period of Luteal Regression1

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Abstract
Patterns of blood flow to the uterus and ovaries of 27 mature Finn-cross ewes were determined during the normal period of luteal regression using radioactive microspheres. Ewes were randomly assigned to equal numbers to receive an intrauterine implant on day 9 of an estrous cycle (day of estrus = day 0) containing either 1) cholesterol (control, C), 2) estradiol-17βcholesterol (E2:C,2:98% by wt), or 3) α-methyl tyrosine (a-MT). The nine ewes in each group (C, E2 :C or α-MT) were randomly assigned to equal numbers to receive microspheres at 0800 hr, and were sacrificed within 2 hr, on days 14, 15 or the first day of estrus following placement of the implants. Venous blood was collected from all ovaries bearing corpora lutea (CL) prior to placement of intrauterine implants on day 9 and within 1 hr following microsphere injection on day 14, 15 or estrus for determination of progesterone by radioimmunoassay. The study failed to demonstrate any effect of uterine implants on estrous cycle length, unilateral uterine or ovarian blood flow or luteal progesterone secretion, regardless of treatment group. Blood flow to uteri of ewes sacrificed at estrus was greater (P<.05) than blood flow to uteri of ewes sacrificed on day 14 or 15 of the estrous cycle. No differences in uterine blood flow were observed between ewes sacrificed on days 14 or 15 postestrus. At estrus, blood flow to the tip of each uterine horn was greater (P<.05) than blood flow to the cervical end of the uterine horns. There was no effect on day of sacrifice (14, 15 or estrus) or treatment (C,E2 :C or α-MT) on ovarian weight. However, ovaries with CL were heavier (P<.05) than ovaries without CL (2.54 ± .09, n = 39; 1.67 ± .16 g, n = 15, respectively). Corpora lutea weights (g) remained constant from day 14 (.54 ± .04, n = 20) to day 15 (.45 ± .02, n = 22) before declining (P<.05) at estrus (.24 ± .02, n = 17). Blood flow to the extraluteal component of ovaries with CL was constant on days 14 to 15 but had increased (P<.05) at estrus. Blood flow to ovaries without CL did not differ on the days studied and averaged .37 ± .09 ml/ min/g of tissue. The amount of blood flow to the CL decreased (P<.01) from day 14 to 15, as well as from day 15 to estrus when only a minimal flow rate was observed. As observed from luteal blood flow, progesterone concentration in venous blood from ovaries with CL decreased (P<.05) from day 14 to 15, and from day 15 to estrus. Evidence that ovarian progesterone secretion is strongly associated with blood flow through the CL is provided by the overall significant correlation (r = .79; P<.01) found to exist between the two measurements. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science